I'm more interested in understanding what is going on in the brain/body rather than arguing over terminology. Both psychological and other factors seem to cause burnout/CFS, although psychological factors do seem to be the most important. Depression is a resulting symptom, not a cause.
Stress and burnout affect different people in different ways: some people get depressed, others develop chronic pain (fibromyalgia, ME), others have chronic fatigue etc.
As for the psychological factors that seem to be important: motivation, goals and emotions all seem to play a large part.
While you're correct that CFS is not entirely psychological (functional would be a better term), it does appear to be mostly caused by psychological factors. If you look at the main triggers for CFS they are: job stress, relationship stress, and viral infection - and there is some doubt as to whether the viral infection is a cause or just a symptom of a weakened immune system.
While I agree with most of what you say, the problem is that a lot of studies have been done on the HPA axis and cortisol in CFS/burnout, but there is no agreement. Some studies find low cortisol, others don't. There is definitely HPA axis dysfunction, but nobody can seem to pin it down. I suspect that if you measured cortisol throughout the day and correlated it to a symptom diary and/or a stress test, you might be able to come up with a diagnostic test.
The other issue is that there is no cheap and easy cortisol test like there is for blood glucose. As far as I can tell it would be possible to develop such a test, but nobody has done it yet for a number of reasons (lack of demand, cost, FDA approval, etc).
If someone were to [1] figure out a definitive test for burnout/CFS and [2] develop/patent a home testing kit they would be very rich and help a lot of people into the bargain.
As for Teitelbaum: while he does have some useful stuff to say, he also peddles a lot of quackery.
Google 'chronic fatigue syndrome' to see what the end-point of burnout is like.
Some warning signs: depression, anxiety, insomnia, loss of appetite, constant illnesses, dreading going into work, racing heartrate, etc. Although to be honest by the time you've got to that point you are already pretty burned out and you're well on your way to CFS.
My solution for the past 10 years has been to live my life so there is little/no possibility of ever having burnout (and it has worked :)
Unfortunately there is no standard blood test for CFS/burnout. I agree with Amy that cortisol might be useful, but the problem is that it isn't always a reliable indicator of illness.
Anyway, just keep doing what you are doing and you will gradually recover. For more info, see: http://www.mind-body-health.net/recovery.html (a site I developed 10 years ago after recovering myself).
Unfortunately this is a very misunderstood area of medicine because doctors (and patients) like to pigeonhole illnesses as either physical or psychological, and psychiatric/psychosomatic illness has a very bad negative stereotype.
Having experienced burnout and resulting chronic fatigue syndrome (which is really just an extreme version of burnout that persists long after the stress has ended), I pretty much agree with everything you say. However it's incorrect to say that burnout is physical rather than psychological as psychological factors do play a large part in determining whether or not you experience burnout.
Stress and burnout affect different people in different ways: some people get depressed, others develop chronic pain (fibromyalgia, ME), others have chronic fatigue etc.
As for the psychological factors that seem to be important: motivation, goals and emotions all seem to play a large part.
While you're correct that CFS is not entirely psychological (functional would be a better term), it does appear to be mostly caused by psychological factors. If you look at the main triggers for CFS they are: job stress, relationship stress, and viral infection - and there is some doubt as to whether the viral infection is a cause or just a symptom of a weakened immune system.